The 192-mile, $1.6 billion project is planned by Eversource Energy in partnership with Hydro-Quebec. The line, with 60 miles buried, would carry enough electricity to power a million homes.

The U.S. Department of Energy this month recommended the project for a presidential permit to cross the Canadian border. State approval from the SEC is seen as essential to the project's advancement.

Northern Pass is one of several transmission lines proposed for Maine, New Hampshire, Vermont, and northern New York. The lines would carry hydro, wind, solar or stored electricity. Hydro-Quebec seems poised to work with whichever transmission project prevails.

The successful generation and transmission partnerships will not only win regulatory approval, but gain coveted power purchase agreements with utilities.

Utilities in Massachusetts, Connecticut and Rhode Island are in the market for long-term clean power contracts. A competitive project evaluation is now underway in Massachusetts, which is eager to meet its greenhouse gas reduction goals.

In a statement, Northern Pass said it is disappointed "considering the review process was already extended by nine months from what was originally a 12-month process" under a New Hampshire law.

The company said it remains confident in its ability to achieve a 2020 in-service date with construction beginning in the second quarter of 2018.

"Further, we are convinced that we have submitted the most mature project into the Massachusetts Clean Energy RFP," an Eversource spokeswoman said.